The present invention relates to a mounting boss for a gas sensor in an exhaust system. More particularly, the present invention relates to a mounting boss and method of making.
Oxygen gas sensors or exhaust constituent sensors have been used in vehicles to sense the presence of constituents (e.g., oxygen, hydrocarbons, nitrous oxides, etc.) in an exhaust gas flow and to sense and/or signal, for example, when an internal combustion engine switches from rich to lean or lean to rich operation.
Because exhaust gas sensors are required to be positioned within an exhaust gas flow, the exhaust gas sensor is usually mounted to a portion of the exhaust system. Furthermore and due to application requirements, the exhaust system itself will have unique exterior configurations, which may not be optimal mounting locations for exhaust sensors (e.g., irregular welding surfaces, angular surfaces, etc.). In addition, and due to the gas sensor mounting location, the sensor is exposed to and must be able to withstand vibration and jarring which occur during vehicle operation as it traverses along rough roads. Accordingly, exhaust system designs and oxygen and/or other gas sensor design limitations limit the positioning and configuration of the gas sensor within an exhaust system. For example and in one application, a prefabricated mounting boss is secured to the exhaust system by an attachment method wherein the boss is inserted into or about a hole pierced in an end cone of the exhaust system and the boss is welded to the end cone using metal inert gas (MIG) welding or projection welding. However, this process requires the application of a separate boss to be welded to a welding surface, which must be flat and the boss is welded about the hole. In addition, the welding of the boss itself to the end cone is not without problems as weld spatter may be found in the threads and there may be anyone of the following; thread distortion, weld skips, or voids, which are created by the welding processes or heat. In addition, and in order to weld such bosses to the exhaust system housing the same must have a sidewall thickness sufficient to have the boss welded thereto.
Accordingly, it is desirable to provide a robust gas sensor mounting boss and method of making wherein the sensor is rigidly secured to a sidewall of the housing.